cornea human

CORNEA

Dr.H.Izar Aziz,SpM(K)*Function of the cornea :as Window of the globe & refractive media:clear & transparent with power + 42 D.as microorganisms barrier

Dr.H.Izar Aziz,SpM(K)

Corneal endothelium maintains corneal clarity through:Acting as a barrier to the aqueous humorProviding metabolic pump*Loss of transparency caused by : endothelial damage epithelial damage.

Corneal EdemaAlteration of endothelial function corneal edemaAcute altered barier effect of the endothelium/epitheliumChronic inadequate endothelial pump*

Causes of Corneal EdemaAcuteTrauma (ex: intraocular surgery)Inflammation Hypoxia (ex: contact lens wear)Increased intraocular pressureChronicTrauma or toxinsFuchs dystrophyPosterior polymorphous dystrophyIridocorneal endothelial syndromeRetained lens fragment*

*Keratitis : isinflammation of cornea ,caused bymicroorganism infectionantigen antibodies / allergic reaction.

*Epithelium covered by tear film :as a barrier microorganisms infection . (except N. Gonorrhoea)Descemets membrane as barrier for bacterial infection to COA .(but not for fungus)

Etiology of keratitis : Exogenous : bacteria ,fungus , virus, parasiteEndogenous : allergic reaction.

*Bacteria :-Pure Pathogen : Streptococcus pneumoniae, Pseudomonas aeroginosa

-Opportunistic bacteria : -Staphylococcus,Moraxella, Serratia(as flora at conjunctiva

. Alcoholic/ B6 deficiency .Topical steroid >>>. Corneal abrasion Pathogen bacteria Corneal infection

*Fungus (usually opportunistic)Candida, Fusarium, AspergillusVirusVHSVVZParasite : Acanthamoeba in Contact lens user

*Symptoms & SignsSubjective (patients history )painglare (photophobia)blur vision tearing (lacrimation)

Objective - loupe or slit lamp examinationblepharospasmeciliary injection tearing (lacrimation)superficial infiltrate or corneal ulcer hypopyon- in advanced cases.

*

*Special examinations : Flourescein test for corneal ulcer Seidel test for perforating cornea

*Laboratory Studies Etiologic diagnosis.Scraping from:infiltrate / edge of the ulcerfornices of conyunctivaSlide Staining :Gram ( for bacteria)Giemsa (for fungus )

*Clinical courseSubepithelial /epithelial keratitisRecover without scar Become corneal ulcerCorneal blindnessrecoverExtirpation of the globeAbulbi Phtysis bulbiPermanent blindness

*Clinical appearance of corneal ulcersSerpeginous corneal ulcer.Etiology : Pneumococcusacute, well circumscribed gray ulcer, tends to spread to center of corneahypopyon is common (sterile)

*Pseudomonas ulcer. Etiology : Pseudomonas aerg. (present in Flourescein sol.) bluish-green exudate very acute ,spread rapidly to all direction ,because proteolytic enzyme destroy the corneal stromadescemetocele

*Marginal Ulcer Etiology : Staphylococcusaffect limbal area Fungal ulcerhistory: agriculture trauma topical steroid usage >>>>gray Infiltratethick hypopyon & irregular surfacesatellite lesions - in endothelium

*Moorens UlcerEtiology : antigen antibodies reactionProgressive excavation of the limbus.

*Treatment atropine eye drops Anti microorganisms depend on laboratory finding (scraping & culture) Antibiotic for bacteriaAnti fungus for fungal infectionAntiviral for viral infectionSteroid for Moorens ulcereye bandage

*Prognosis depends on :depth & width of the ulcer Corneal scar

Dr.H.Izar Aziz,SpM(K)*NebulaMakulaLeukomaLeukoma adherentCentral ,-->corneal blindness-Periphery (No visual disturbance )

Dr.H.Izar Aziz,SpM(K)

Dr.H.Izar Aziz,SpM(K)*PreventionAvoid corneal traumaAvoid overuse of topical steroid Cure external eye infection as soon as possible.Avoid trigger factor for relapsing H.simplex keratitis.

Dr.H.Izar Aziz,SpM(K)

KeratoconusA progressive thinning and bulging of the central of paracentral cornea cone shape cornea6-8% cases: positive family historyOnset: around puberty

Clinical Findings Unilateral High astigmatism and myopic blurred visionMunson sign: bulging of the lower lid in downgaze

Treatment SpectaclesRigid contact lens Keratoplasty

*Reference BooksVaughn D, Asbury T; General Ophthalmology, 15th edition, Appleton & LangeMiller S; Parsons Diseases of the eye, 17 th Edition, Churcill Livingstone, 1984Kanski JJ, Clinical Ophthalmology, 4th edition,Oxford Butter Worth Heineman Ltd, 1999

*